1. Field of the Invention
The present invention relates to a vacuum-generating unit which is capable of supplying a negative pressure to a suction means including, for example, a suction pad.
2. Description of the Related Art
A vacuum-generating unit has been hitherto utilized as a means for supplying a negative pressure to a suction pad. Such a vacuum-generating unit generally comprises, for example, an ejector which is used to generate the negative pressure, a vacuum port which is connected in communication with a suction means such as a suction pad via a tube, a valve mechanism section which is provided with a pressure fluid-supplying solenoid-operated valve and a vacuum-breaking solenoid-operated valve for supplying and shutting off the compressed air with respect to the ejector and the vacuum port respectively, and a vacuum switch section which is used to detect the negative pressure generated at the vacuum port.
The operation of the vacuum-generating unit concerning the conventional technique as described above will be schematically explained.
The compressed air is supplied via the valve mechanism section to the ejector to generate the negative pressure. The negative pressure, which is generated by the ejector, is fed to the suction pad via the tube connected to the vacuum port. A workpiece is attracted in accordance with the action of the negative pressure generated at the suction pad. The workpiece, which is attracted and held by the suction pad, is transported to a predetermined position in accordance with a displacement action of a robot arm.
Subsequently, the workpiece, which is held by the suction pad, is disengaged therefrom when the compressed air (positive pressure) is fed from the valve mechanism section to the suction pad via the passage communicating with the vacuum port. Accordingly, the suction pad is released from the negative pressure state. As a result, the workpiece is separated from the suction pad, and it is transported to a desired position.
It has been hitherto demanded that the entire apparatus has a small size and a light weight as far as possible by reducing the dimension of the main body section in the widthwise direction substantially perpendicular to the longitudinal direction, because of the following reason. That is, for example, when a plurality of vacuum-generating units are interlocked with each other to form a manifold, if the dimension of the main body section in the widthwise direction is reduced, then it is possible to obtain a solenoid-operated valve manifold having an extremely small size and a light weight, and it is possible to effectively utilize the space of installation.
A general object of the present invention is to provide a vacuum-generating unit which makes it possible to realize a small size and a light weight by reducing the dimension of a main body section in the widthwise direction substantially perpendicular to the longitudinal direction.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.